Epstein-Barr virus (EBV) is a double-stranded DNA virus with tropism for some epithelial cells and for B lymphocytes. The entire nucleotide sequence of EBV strain B95-8 has been published (Baer et al., Nature 310:207; 1984). From this sequence, it was predicted that EBV has 84 major open reading frames (ORFs). Certain EBV ORFs have been identified as encoding specific viral proteins, however, many ORFs have not been associated with specific viral proteins.
Several groups have investigated an ORF present in the Bam H1 Z fragment of EBV, referred to as BZLF2. Cohen et al. (Proc. Natl. Acad. Sci. USA 81:4183, 1984) reported that the Bam H1 Z fragment encoded three peptides ranging in size from 77 to 31 kD. Seible et al. (Proc. Natl. Acad. Sci. USA 60:902, 1986) detected the presence of a 140 kD protein in EBV-infected cells which they attributed to a BZLF2 ORF. In contrast, Baer et al. predicted an approximate molecular weight of 25 kD for a protein encoded by the BZLF2 ORF.
None of the studies demonstrated the function of the protein they predicted to be encoded in the Bam HI Z fragment, and none of the proteins disclosed in the prior art correlated to any of the proteins known to be present in purified EBV or directly involved in replication of the virus or transformation of cells by EBV. Thus, prior to the present invention, there was a need in the art to establish the actual amino acid sequence and size of a protein encoded by the BZLF2 ORF, and to determine the function of the protein.